Dynamic Odd–Even Effect in Liquid n‐Alkanes near Their Melting Points

n‐Alkanes are the textbook examples of the odd–even effect: The difference in the periodic packing of odd‐ and even‐numbered n‐alkane solids results in odd–even variation of their melting points. However, in the liquid state, in which this packing difference is not obvious, it seems natural to assume that the odd–even effect does not exist, as supported by the monotonic dependence of the boiling points of n‐alkanes on the chain length. Herein, we report a surprising odd–even effect in the translational diffusional dynamic properties of n‐alkanes in their liquid states. To measure the dynamics of the molecules, we performed quasi‐elastic neutron scattering measurements near their melting points. We found that odd‐numbered n‐alkanes exhibit up to 30 times slower dynamics than even‐numbered n‐alkanes near their respective melting points. Our results suggest that, although n‐alkanes are the simplest hydrocarbons, their dynamic properties are extremely sensitive to the number of carbon atoms.     

Construction and assessment of some perchlorate-selective liquid membrane electrodes

Perchlorate-selective liquid membrane electrodes were developed by incorporating the ion-pair complexes of perchlorate with brucine, cinchonidine, emetine and benzyldimethyltetradecylammonium chloride (zephiramine) in nitrobenzene. The electrodes, which respond to perchlorate ion over the concentration range 1.0–5.0 × 10^?4 M ClO^?₄, have a fast response and wide pH range. The zephiramine-perchlorate electrode was the best in terms of its fast response, wide pH range and high reproducibility of potentials. Most common inorganic and organic anions, except permanganate, do not cause significant interference. Electrodes based on brucine-, emetine- and zephiramine-perchlorate were successfully employed for the direct potentiometric determination of perchlorate in the presence of halides, sulphate, nitrate and chlorate. The cinchonidine-perchlorate electrode showed comparatively poor selectivity.     

A facile synthesis and spectral (ir, 1H, 13C, 31P nmr) studies of 2,10-dichloro-6-aryloxy-12H-dibenzo[d,g][1,3,2]dioxaphosphocin 6-sulfides

The synthesis of new 2,10-dichloro-6-aryloxy-12H-dibenzo[d,g][1,3,2]dioxaphosphocin 6-sulfides 4 was achieved in two steps with high yields from the simple materials 5,5′-dichloro-2,2′-dihydroxydiphenyl-methane (1) and thiophosphoryl chloride (2) which produced the key intermediate 2,6,10-trichloro-12H-dibenzo[d,g][1,3,2]dioxaphosphocin 6-sulfide (3) . Treatment of 3 with substituted phenols under phase transfer catalytic (PTC) conditions led to members of 4 . Long range coupling [⁵J_(P,H) = 3.6 Hz] was observed between phosphorus and one of the bridged methylene protons in 4 . A ¹³C nmr analysis revealed ²J_(P,O,C), ³J_(P,O,C) ⁴J(P,O,C) and ⁵J(P,O,C) couplings. All ³¹P nmr chemical shifts for thirteen members of these new heterocycles are reported for the first time. The nmr data are not totally definitive to confirm a boat-chair as the major conformer for the central eight-membered dioxaphosphocin ring, but such a conformer is tentatively suggested as favored.     

Design and characterization of a modified WDM ring network – An analytical approach

The present paper proposes the design of a modified ring network topology with a significant improvement in average delay and blocking probability over the simple ring network. The backbone ring network is modified by connecting the alternate nodes in regions identified statistically as of high traffic density. A mathematical model for the proposed modified network has been developed to investigate the blocking probability and average delay as the data traverses from source to destination. The analysis reports an improvement in the average delay performance with the inception of call priority at the processing node and thus provides a scope to implement the given grade of service.     

Nanoporous morphology of alumina films prepared by sol–gel dip coating method on alumina substrate

Nanoporous crack free alumina thin films were fabricated in two phases gamma (??) and alpha (??) by sol?Cgel dip coating method. The thickness of the mesoporous films was increased with binder by varying its concentration, and with increasing the number of coating. The porosity, pore size, surface area and phase were controlled by sintering temperature. Interconnected pore structure of 8?C15?nm diameter were successfully prepared by repeating the deposition several times. FESEM, BET, AFM and XRD techniques were employed for the microstructural characterization.     

Bianchi Type-IX String Cosmological Models for Perfect Fluid Distribution in General Relativity

The present study deals with Bianchi type-IX string cosmological models for perfect fluid distribution. We consider two cases： （i） ρ ＋ λ = 0, （ii） ρ - λ = 0, where ρ and λ are the rest energy density and the tension density of a string cloud, respectively. The physical and geometrical properties of the models are discussed.     

Microstructure, chemical bonds, and friction properties of nanocrystalline diamond films deposited in two different plasma media

Nanocrystalline diamond films with the properties dependent on the composition of the gaseous medium have been prepared using the microwave plasma enhanced chemical vapor deposition (MPECVD) method. A nanocrystalline film formed in the Ar/CH₄ plasma is characterized by a high crystallinity factor, a small grain size, a large fraction of sp ²-amorphous carbon, and, consequently, by an increase in the hardness and elastic modulus. The low value of the friction coefficient of this film is associated with the small grain size and large fraction of the sp ²-amorphous carbon boundary phase that ensures an easy sliding. The contact angle of the film is small (hydrophilic properties) in the case when the plasma consists of an Ar/CH₄ mixture. It has been shown that the wetting properties of the films are provided by a thin layer of carboxyl and hydroxyl functional groups passivating the dangling bonds at the surface that are responsible for the boundary lubrication mechanism. It has also been found that the friction coefficient of these films is inversely proportional to the contact pressure dependent on the diameter of the sliding counterbody ball.     

Effect of tin-doping on polytypism of melt-grown crystals of cadmium iodide

The effect of doping of metallic tin in cadmium iodide crystals has been systematically studied. The method of zone melting has been employed both for purification and for the growth of single crystals of cadmium iodide. The doping has been carried out by zone levelling technique. The as-grown crystals have been characterized by X-ray diffraction and physical methods. All the crystals have been found to consist of the most common polytype 4H. Unlike the case of pure undoped crystals of cadmium iodide grown from melt, all the X-ray photographs showed the presence of arcing. None of the photographs showed the presence of streaking. Besides, the doped crystal were found to be harder than the crystals of undoped cadmium iodide. Unlike the undoped crystals, cleavage in the doped crystals was found to be difficult and highly localized. The results have been discussed.